This study will test the hypothesis that the circadian rhythm of sleep is altered in major depressive disorder (MDD) compared to age and sex matched control subjects. The study will focus on coordination of wakefulness to sleep. It is hypothesized that sleep onset differences will include: 1)higher beta and lower delta EEG activity; 2)elevated core body temperature, a decreased rate of decline in core body temperature; 3)delayed melatonin secretion, increase cortisol secretion, diminished sleep-related growth hormone secretion. 5M01RR00056-39-0649 This study proposes to obtain pilot data on the effects of chronic and alcohol consumption on benzodiazepine receptor (BZR) distribution and density in adolescent onset alcohol dependence using [11C] flumazenil binding visualized by PET. Alterations in the gamma-aminobutyric acid (GABA) neurotransmitter system induced by chronic alcohol consumption represent the mostly likely neurochemical substrate of alcohol dependence. Subjects with adolescent-onset alcohol use disorders, compared with controls, will show reduced binding of [11C]-flumazenil in the cingulate cortex.